For its part, Pyongyang over the weekend threatened war with any nation that stops North Korean ships on the high seas and attempts to inspect them for illicit nuclear or weapons shipments. Such inspections would be allowed under the terms of the UN Security Council resolution.

North Korea also vowed to turn into weapons-usable material its small stockpile of plutonium and acknowledged that it has a uranium enrichment program, as the US has long suspected.

The sanctions passed by Security Council members Friday are a mixture of trade and financial restrictions designed to stop North Korea's weapons development. They echo measures included in previous UN resolutions. The difference this time, say administration officials and experts outside government, is that Russia, China, and other nations that in the past have been reluctant to enforce sanctions are now convinced of their necessity.

North Korea's underground nuclear test – its second such experiment – and recent string of ballistic missile tests has convinced even the hesitant that Pyongyang's real goal may be to develop a nuclear arsenal.

That does not necessarily mean that the US and the rest of the world are now aiming to use force to interdict North Korean ships on the high seas.

Many countries would be reluctant to take such a fateful step, said Victor Cha, a Korea expert at the Center for Strategic and International Studies at a Friday press briefing. But there are other things that could be done, including heightened customs inspections, more thorough cargo container inspections, and scrutiny when ships stop along the way to their final destinations.

There are many things "in this resolution that take us further down the road of an effective inspection regime," said Mr. Cha.

It is against this background that South Korea's President Lee will arrive in the US on a previously scheduled official visit.

Lee is scheduled to meet with President Obama in the White House Tuesday. He will also meet with cabinet secretaries and congressional leaders.

While trade and other items likely will be discussed, it is the North Korean threat that will be on the top of Lee's agenda in the US.

President Lee has made it clear that any further assistance from relatively rich South Korea to impoverished North Korea will depend on progress in the six-party talks on Pyongyang's nuclear program.